Arizona drought prompts unusual Colorado River water proposal

Give up some water now to avoid cuts later

Arizona may leave part of its annual share of Colorado River water in Lake Mead next year, taking a calculated gamble that giving up some water now will help it avoid deeper losses later.

Under a plan now being considered, water officials would pass up billions of gallons that they could take from the river in 2011, hoping to keep the drought-stricken reservoir full enough to avoid triggering automatic cutbacks. Any cutbacks could deny Arizona and Nevada even more water in 2012.

The sacrifice would be relatively small - 80,000 acre-feet out of Arizona's annual share of 2.8 million acre-feet - and it would barely be missed. Officials would take all of it from a portion of the water set aside for underground water storage, leaving consumers, cities and farmers unaffected.

Still, the attempt to prop up Lake Mead's supply underscores how times have changed for a state that worked so hard for so many years to take every drop of river water it could.

The Central Arizona Project Canal, built to deliver water to the state's biggest cities hundreds of miles from the Colorado, also allowed Arizona to tap a huge unused amount of its share of river water. The state created an underground water-banking system, pouring its extra water on the ground and letting it soak into aquifers, as a way of making sure the entire share was used each year rather than let California take it.

Arizona hopes that cutting back on banking extra water will buy it security as Lake Mead, already 130 feet below its highest level, continues to decline. Some projections say the reservoir within two to three years could shrink to a level that would force cutbacks, shutting off supplies to farmers in central Arizona.

The move also would drive home how tight drought's grip has become on the river. Water managers already have tried to stretch supplies by desalting agricultural runoff, paying farmers to fallow land and building a new reservoir to capture wasted water. But never before have Arizona officials set out to give up some water.

Now, the state and its neighbors on the river just want to get by one year at a time, hoping next year is the one when the drought ends, the river swells and the lake level begins to recover.

"If we leave a little water this year, we won't take the bigger hit the next year," said Larry Dozier, deputy general manager of the Central Arizona Project, the water agency most at risk of losing water to rationing. "Then we can take another spin on Mother Nature's roulette wheel and see what happens."

A simple plan

The potential for the river's first official shortage dominated conversations at the Colorado River Water Users Association conference this month in Las Vegas. Interior Secretary Ken Salazar acknowledged that "the countless communities that rely on the river to sustain them are being forced to make tough choices at a time with few obvious solutions in sight."

Finding a solution, he suggested, "means balancing what's best for one party in the short term with what's best for the Colorado River Basin in the long term."

Arizona's plan to leave water in Lake Mead was devised as such a trade-off, officials say. The idea is almost as simple as it sounds. With the approval of its elected board, the CAP would reduce by as much as 80,000 acre-feet of the water diverted from the river into the 336-mile canal that connects the Colorado to Phoenix and Tucson.

An acre-foot is 325,851 gallons, enough to serve two average households for one year.

The amount is a fraction of the 1.6 million acre-feet the canal moves annually, but it would save 1 foot of elevation at Lake Mead, whose water levels determine when and if drought restrictions take effect under a 2007 agreement among the seven Colorado River states.

The decision to declare a shortage would be made in August based on runoff into the river from winter snow. The Bureau of Reclamation would make a recommendation, and the Interior secretary would decide whether to accept it.

The first shortage trigger is at elevation 1,075 feet above sea level, about 10 feet below the reservoir's current level. At that trigger level, water deliveries to the river's lower basin - Arizona, Nevada and California - are reduced by 323,000 acre-feet for at least one year.

Almost all of that water would be taken from the CAP's allocation for Arizona because of an agreement forged with California more than 40 years ago. To secure California's votes in Congress for construction of the CAP Canal, Arizona agreed that the water in the canal could be used to guarantee California's full allocation in any future shortages.

Nevada agreed to absorb a small amount of the shortage as part of a separate water-banking arrangement with Arizona.

The water Arizona would forgo would have gone toward the state water bank, which stores unallocated water from the Colorado River as a hedge against long-term water shortages.

If Lake Mead sinks low enough to trigger a shortage, some water users would feel the effects, but the CAP supply still has a big enough cushion to protect Phoenix, Tucson and the other cities that use the water.

Even in a third-stage shortage, which would be declared if the reservoir dropped an additional 50 feet, the primary municipal supplies would remain untouched. Phoenix, Tucson and other cities would give up no water.

Economic decisions

At risk in the first stage is the so-called excess pool, water sold mainly to farmers and to cities that want to store it underground for use later. In 2009, for example, Gilbert bought about 100,000 acre-feet and deposited most of it in underground storage banks.

Agricultural users in Maricopa, Pinal and Pima counties would lose access to some water under a first-stage shortage, but the threats are greater as Lake Mead shrinks further. A third-stage drought could reduce supplies to farmers by nearly half.

"We would go back to pumping more groundwater," said Brian Betcher, general manager of the Maricopa-Stanfield Irrigation and Drainage District in Pinal County.

With access to CAP water, he said, "we've been able to leave a lot of water underground just for this event."

"It only becomes a matter of what it costs to pump it, but the water is there."

Farmers would have ample time to prepare, Betcher said. Some could decide to replace any lost CAP water with groundwater. Others could decide to grow different crops or even fallow some land if the cost of pumping water outweighed the expected return from the cotton, wheat, alfalfa or other crops.

"It's a market situation," he said. "Growers have to make economic decisions about how much they can farm and what crops will work for them."

Decision day

Arizona will decide whether to forgo water by April, based on preliminary runoff projections, but the state won't know if its plan works until August, when final runoff figures are in place and projected lake levels are released.

If thiswinter is unusually dry, Arizona could give up its water and still face drought restrictions, though the Colorado River may benefit from a series of early-winter storms that have plastered the Rocky Mountains, the source of most of the river's flow.

Other factors could figure into the decision. Extra water could be released from Lake Powell, which is upstream from Lake Mead, depending on how much runoff flows down the river. Mexico has agreed to store some of its allocation in Lake Mead while farmers on the border work to recover from an earthquake, a step that could reduce the reservoir's decline by as much as 3 feet.

Any measure has to comply with the laws and agreements that govern the Colorado River, said Terry Fulp, the deputy director of the bureau's lower Colorado region. The 2007 plan is not as popular among some water users now that its terms lead toward shortage, but it guides the river's management at least through 2025.

"These kinds of agreements are the results of a lot of compromise," he said. "Once you bend or break one, all of them are on the table to be bent or broken, and before you know it, there's no agreement."

Herb Guenther, director of the Arizona Department of Water Resources, said the seven river states remain committed to the 2007 drought plan, even as a shortage looms.

"We're going to be as frugal as we possibly can in trying to keep as much water in there as possible," he said. "You have to remember, even after an 11-year drought, we've still got half the storage on the river we started with. We've been planning for these long-term droughts for over 30 years now, and as a desert state, we're as secure as any state in the nation."